Class-E Inductive Heating Circuit for Battery-Powered Aerosol Substrates
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Solution Overview
Problem
There is a need for an induction heating device capable of heating aerosol-forming substrates, particularly solid substrates, without an external power supply, that is compact, easy to use, and can rapidly generate heat for on-demand aerosol production in smoking articles.
Innovation Solution
The device employs a DC power source, a Class-E power amplifier, and an LC load network with a helically wound inductor coil to induce heat in a magnetically permeable and electrically conductive susceptor, which transfers heat to the aerosol-forming substrate, using a cavity for inductive coupling and a microcontroller for temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional combustion heating is used, then heat can be generated, but combustion temperatures exceed 800°C causing inefficient oxidation and harmful pyrolysis products
Solution Approach 1:
The patent replaces the mechanical combustion system with an electromagnetic induction heating system. The induction heating device generates an alternating magnetic field that induces eddy currents in the susceptor, converting electromagnetic energy directly into heat without combustion. This substitution eliminates the harmful oxidation and pyrolysis products while achieving the required heating temperature for aerosol formation.
Solution Approach 2:
The patent changes the heating mechanism from combustion-based thermal transfer to electromagnetic induction heating. By using a susceptor material with specific magnetic properties (magnetic permeability and electrical conductivity), the system achieves rapid heating at controlled temperatures (200-400°C) well below combustion temperatures, preventing the formation of harmful pyrolysis products while efficiently generating aerosol.
2Productivity
If induction heating is implemented, then rapid heat generation is achieved, but the device requires external power supply and complex circuitry
Solution Approach 1:
The patent combines the power source (rechargeable battery) and the induction heating circuit into a single integrated portable device. The Class-E power amplifier and LC load network are miniaturized and housed together with the battery, eliminating the need for external power supplies. This merging enables rapid heat generation (heating the susceptor to operating temperature in seconds) while maintaining device portability and simplicity.
3Loss of energy
If a susceptor is used for induction heating, then efficient heat transfer to the substrate is achieved, but the susceptor material selection becomes constrained
Solution Approach 1:
The patent employs composite material structures for the susceptor, combining materials with complementary properties. The susceptor may consist of multiple layers or combinations of magnetic particles embedded in a matrix material, allowing optimization of both magnetic permeability and electrical conductivity. This composite approach enables efficient induction heating while providing flexibility in material selection and formulation to suit different aerosol-forming substrate requirements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration allows for efficient, rapid heating of the susceptor to 350-400°C in under five seconds, with a compact design and low inductor temperature, enabling the production of aerosols at 200-240°C, and is powered by rechargeable batteries for convenience and environmental sustainability.
Implementation Method 1
The susceptor of the tobacco-laden substrate is exposed to an alternating magnetic field generated by an induction source, so that an alternating magnetic field is induced in the susceptor. This induced alternating magnetic field generates heat in the susceptor
Implementation Method 2
an alternating magnetic field is induced in the susceptor. This induced alternating magnetic field generates heat in the susceptor
Implementation Method 3
at least some of this heat generated in the susceptor is transferred from the susceptor to the aerosol-forming substrate arranged in thermal proximity to the susceptor to produce the aerosol
Data Source
Figure 1
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Figure 3
AI summary
An inductive heating device (1) comprises: a device housing (10), a DC power source (11), a power supply electronics (13) comprising a DC/AC inverter (132) including a Class-E power amplifier with a transistor switch (1320), a transistor switch driver circuit (1322), and an LC load network (1323) configured to operate at low ohmic load (1324), the LC load network (1323) comprising a shunt capacitor (CI) and a series connection of a capacitor (C2) and an inductor (L2), and a cavity (14) arranged in the device housing (10), the cavity (14) having an internal surface shaped to accommodate at least a portion of the aerosol-forming substrate (20), wherein the cavity (14) is arranged such that the inductor (L2) is inductively coupled to the susceptor (21) of the aerosol-forming substrate (20) during operation.